A control signal generation circuit includes: a first circuit unit which controls, according to inputted video signals, light-up amount of each pixel of a display panel where a plurality of pixels constituted by including a white sub-pixel are disposed; and a second circuit unit which controls luminance of a backlight that lights up the display panel from a back surface. The second circuit unit calculates a saturation feature value in one frame from the saturation value of each pixel, generates a signal for controlling the luminance of the backlight based thereupon, and calculates a luminance increase rate by using the saturation value of each pixel and the saturation feature value. The first circuit unit performs luminance decreasing processing of each pixel according to the luminance increase rate, and supplements the saturation of each pixel according to the light-up amount of the white sub-pixels.
Legal claims defining the scope of protection. Each claim is shown in both the original legal language and a plain English translation.
1. A control signal generation circuit, comprising: a first circuit unit which controls, according to an inputted video signal, light-up amount of each pixel of a display panel where a plurality of pixels constituted by including a white sub-pixel are disposed; and a second circuit unit which controls luminance of a backlight that lights up the display panel from a back surface, wherein the second circuit unit comprises, an each-pixel saturation calculation circuit which calculates a saturation value of each pixel, a feature value/luminance decrease amount calculation circuit which calculates a saturation feature value in one frame by using the saturation value of each pixel, and calculates luminance decrease amount of the backlight based thereupon, a PWM signal generation circuit which generates a signal for controlling the luminance of the backlight based on the luminance decrease amount of the backlight, and transmits the generated signal towards the backlight, and an each-pixel luminance increase rate calculation circuit which calculates a luminance increase rate of each pixel by using the saturation value of each pixel and the saturation feature value; and wherein the first circuit unit comprises a saturation supplementing circuit which supplements the saturation of each pixel according to the light-up amount of the white sub-pixel, wherein the feature value/luminance decrease amount calculation circuit calculates the luminance decrease amount of the backlight as a small value in a case where the video signal is a case of a high saturation color display, calculates the luminance decrease amount of the backlight as a large value in a case where the video signal is a case of low saturation color display or a case of intermediate saturation color display containing primary color display in a part thereof, and calculates the luminance decrease amount of the backlight as a small value in a case where the video signal is a case of achromatic display containing primary color display in a part thereof.
A display control circuit adjusts brightness in a display with white sub-pixels. It has two main parts: a pixel controller and a backlight controller. The pixel controller adjusts the brightness of each pixel based on the input video. The backlight controller dims the backlight to save power and enhance contrast. This backlight controller calculates a "saturation feature value" for each frame based on pixel saturation. It dims the backlight more for low/mid saturation and less for high saturation or achromatic (grayscale) content. The pixel controller boosts the saturation of each pixel to compensate for backlight dimming, especially relying on the white sub-pixels, preventing washed-out colors.
2. The control signal generation circuit as claimed in claim 1 , wherein the first circuit unit further comprises an each-pixel luminance decreasing circuit which performs luminance decreasing processing of each pixel according to the luminance increase rate.
The display control circuit described in Claim 1 includes a pixel-level luminance reduction component. In addition to the pixel and backlight control functionality already described, the pixel controller reduces the brightness of each pixel based on a calculated "luminance increase rate". This increase rate is determined using individual pixel saturation and the frame's saturation feature value. This luminance decrease compensates for the increased saturation ensuring that overall brightness levels remain consistent, and that contrast is enhanced.
3. The control signal generation circuit as claimed in claim 1 , wherein the feature value/luminance decrease amount calculation circuit comprises: an each-pixel saturation judging section which judges whether the saturation value of each pixel is larger or smaller with respect to a saturation threshold value set in advance; an each-pixel saturation deviation sum calculation section which individually calculates sum total of saturation deviation regarding a case where the saturation value is judged as being equal to or less than the saturation threshold value and a case where the saturation value is judged as being larger than the saturation threshold value, by the each-pixel saturation judging section, respectively; a total-pixel saturation deviation average calculation section which calculates a saturation deviation average value of total pixels by using the sum total of the each saturation deviation and number of resolution of the display panel; and a saturation feature value calculation section which calculates the saturation feature value by using the saturation deviation average value of the total pixels, a saturation maximum value of the total pixels, and a coefficient regarding luminance control of the backlight.
The display control circuit from Claim 1 calculates the "saturation feature value" as follows: It compares each pixel's saturation to a preset threshold. It calculates separate sums of "saturation deviation" above and below this threshold. These sums are then averaged to get a saturation deviation average for all pixels. Finally, it calculates the saturation feature value using this average, the maximum saturation value of all pixels, and a coefficient that controls how the backlight responds to saturation. This feature value is then used to dim the backlight intelligently.
4. The control signal generation circuit as claimed in claim 3 , wherein the feature value/luminance decrease amount calculation circuit calculates the luminance decrease amount of the backlight to be a small value according to an average value of the saturation value of each pixel in a case where the average value is a higher value than the saturation threshold value, calculates the luminance decrease amount to increase continuously as the average value becomes decreased until reaching the saturation threshold value from the higher value, calculates the luminance decrease amount to decrease continuously as the average value becomes decreased after exceeding the saturation threshold value, and calculates the luminance decrease amount to continue at the saturation threshold value.
Building on the method described in Claim 3, the backlight dimming behavior of the display control circuit operates as follows: When the average saturation of all pixels is high (above the saturation threshold), the backlight is dimmed a small amount. As the average saturation decreases towards the threshold, the backlight dimming *increases*. Once the average saturation goes *below* the threshold, further decreases in saturation cause the backlight dimming to *decrease*. The dimming level then remains constant at the dimming level corresponding to the saturation threshold. This creates an optimal dimming profile based on average saturation.
5. The control signal generation circuit as claimed in claim 3 , wherein provided that the sum totals of the each saturation deviation are defined as Xa, Xb, the saturation threshold value is defined as a coefficient A (0<A<1), the saturation value of k-th (k is an arbitrary value from 1 to the number of resolution) pixel is defined as chroma(k), the feature value/luminance decrease amount calculation circuit calculates value of Xa by applying a numerical expression Xa=Σ{1−(1/A)×chroma (k)} in a case where the chroma(k) is equal to or less than the coefficient A, calculates value of Xb by applying a numerical expression Xb=Σ{1/(1−A)}×(chroma (k)−A) in a case where the chroma(k) is larger than the coefficient A, and calculates a quotient acquired by dividing the sum totals by the number of resolution as the saturation deviation average value of the total pixels.
Expanding on Claim 3, the display control circuit calculates the saturation deviations using specific formulas. If a pixel's saturation (chroma(k)) is below a threshold A, its deviation is 1 - (1/A) * chroma(k). If it's above A, the deviation is (1/(1-A)) * (chroma(k) - A). These deviations are summed (Xa and Xb respectively), and the sum is divided by the number of pixels to get the average saturation deviation. This precisely quantifies how much the pixel saturations deviate around the threshold, informing the backlight dimming.
6. The control signal generation circuit as claimed in claim 5 , wherein provided that the saturation deviation average value of the total pixels is defined as DAVE, a saturation maximum value of the total pixels is defined as MAX(chroma), the saturation feature value is defined as Rank, and a coefficient regarding luminance control of the backlight is defined as B (0<B<1), the feature value/luminance decrease amount calculation circuit calculates the saturation feature value based on a numerical expression Rank=MAX(chroma)×{B×DAVE+(1−B)}.
Using the deviation value (DAVE) from Claim 5, and maximum saturation (MAX(chroma)) from Claim 3, the display control circuit calculates the saturation feature value (Rank) using: Rank = MAX(chroma) * {B * DAVE + (1 - B)}. B is a coefficient between 0 and 1 that controls how much the average deviation influences the final "Rank" value, which represents overall image saturation and is used to dim the backlight.
7. The control signal generation circuit as claimed in claim 6 , wherein the feature value/luminance decrease amount calculation circuit calculates a PWM value PWM used for the luminance control of the backlight from a numerical expression PWM=1/{C−(C−1)×Rank} by using another coefficient C (1≦C≦2) regarding the luminance control of the backlight, and calculates the luminance decrease amount of the backlight based on the PWM value.
Building on Claim 6, the display control circuit determines the backlight dimming amount as follows: A PWM (Pulse Width Modulation) value is calculated using PWM = 1/{C - (C-1) * Rank}, where Rank is the saturation feature value, and C is another coefficient (1 to 2). The PWM value directly controls the backlight brightness. This formula maps the saturation feature value to a specific dimming level.
8. The control signal generation circuit as claimed in claim 7 , wherein in a case where a ratio between the maximum white luminance of the white sub-pixel and the maximum white luminance generated by the video signal is 1:1, the feature value/luminance decrease amount calculation circuit sets the another coefficient C as a value that is twice a ratio of an aperture area of sub-pixels of an RGBW-type display panel with respect to an aperture area of sub-pixels of an RGB-type display panel.
With the dimming equation from Claim 7, the display control circuit configures the coefficient 'C' to optimize backlight control when the white sub-pixel is 1:1 with white from other colors. Coefficient 'C' is set to twice the ratio of the aperture area of RGBW sub-pixels to the aperture area of RGB sub-pixels. Therefore if RGBW sub-pixels are 1.5x the area of RGB sub-pixels, the coefficient 'C' will be set to 3 (2*1.5).
9. The control signal generation circuit as claimed in claim 3 , wherein the saturation threshold value is set as a value that is larger than 0 and equal to or smaller than 0.5.
In the configuration from Claim 3, the saturation threshold value used to compare pixel saturation is set to a value greater than 0, but less than or equal to 0.5. Therefore the saturation threshold will be a value between 0 < A <= 0.5.
10. The control signal generation circuit as claimed in claim 3 , wherein the coefficient regarding the luminance control of the backlight is set as a value acquired by subtracting the saturation threshold value from 1.
As described in claim 3, the coefficient for luminance control is set to a value acquired by subtracting the saturation threshold value from 1. Therefore, if the saturation threshold is 0.3 (A=0.3), the luminance control coefficient is 0.7 (B=1-A=0.7)
11. The control signal generation circuit as claimed in claim 1 , wherein provided that a ratio of an aperture area of sub-pixels of an RGBW-type display panel with respect to an aperture area of sub-pixels of an RGB-type display panel is defined as Y, and a ratio of a maximum white luminance of the white sub-pixels and a maximum white luminance generated by the video signal is p:q, the feature value/luminance decrease amount calculation circuit calculates the another coefficient C from a numerical expression C=(1+(p/q))×Y, and uses the acquired value for calculating the PWM value.
A display panel control circuit calculates the 'C' coefficient used in calculating the PWM (Pulse Width Modulation) value, which controls backlight dimming, as follows: C = (1 + (p/q)) * Y. 'Y' is the ratio of the RGBW subpixel aperture area to the standard RGB subpixel area, while p/q represents the ratio of the maximum white luminance of the white sub-pixel to the maximum white luminance produced by the video signal.
12. The control signal generation circuit as claimed in claim 11 , wherein in a case where the ratio between the maximum white luminance of the white sub-pixels and the maximum white luminance generated by the video signal is p:q, and a ratio thereof p/q is larger than 1, the saturation value of each pixel is defined as chroma(c), a coefficient α is calculated from a numerical expression α=1+((p/q)−1)×(1−chroma(c)), and the coefficient α is used for calculation of saturation supplement and for calculation of the luminance of the white sub-pixels.
Building upon Claim 11, when the white luminance ratio (p/q) is greater than 1, the display panel adjusts color saturation and white subpixel brightness: A coefficient alpha (α) is calculated: α = 1 + ((p/q) - 1) * (1 - chroma(c)). Here, chroma(c) is the saturation value of each pixel. This coefficient α is then used to increase the saturation of the pixel and to calculate how much the white subpixel contributes to the overall brightness.
13. The control signal generation circuit as claimed in claim 11 , wherein in a case where a ratio between the maximum white luminance of the white sub-pixels and the maximum white luminance generated by the video signal is p:q, and a ratio thereof p/q is larger than 2, the saturation value of each pixel is defined as chroma(c), a coefficient α is calculated from a numerical expression α=1+((p/q)−1)×((1−chroma(c))^(p/q)), and the coefficient α is used for calculation of saturation supplement and for calculation of the luminance of the white sub-pixels.
Expanding on Claim 11, When the white luminance ratio (p/q) is greater than 2, the display panel calculates a color adjustment factor 'alpha' to improve color quality. A coefficient alpha (α) is calculated: α = 1 + ((p/q) - 1) * ((1 - chroma(c))^(p/q)). Here, chroma(c) is the saturation value of each pixel. This coefficient α is then used to increase the saturation of the pixel and to calculate how much the white subpixel contributes to the overall brightness. This modified formula handles larger white boost ratios for better color accuracy.
14. The control signal generation circuit as claimed in claim 11 , wherein in a case where a ratio between the maximum white luminance of the white sub-pixels and the maximum white luminance generated by the video signal is p:q, and a ratio thereof p/q is larger than 1, a function of the saturation values calculated from each pixel in one frame is defined as f(x), a coefficient β is calculated from a numerical expression β=1+((p/q)−1)×f(x), and the coefficient β is used for calculation of each-pixel luminance decrease.
Expanding on Claim 11, when the ratio (p/q) of white sub-pixel luminance to generated white luminance is greater than 1, the display control circuit calculates a coefficient β to adjust pixel luminance. β is calculated as: β = 1 + ((p/q) - 1) * f(x), where f(x) is a function of the saturation values of each pixel in a frame. This coefficient β is then used to reduce the brightness of each pixel.
15. The control signal generation circuit as claimed in claim 14 , wherein the function f(x) is calculated from a numerical expression f(x)=(chromaAVE)^E provided that E is a coefficient within a range of 0<E<2 and chromaAVE is an average value of the saturation value of each pixel in one frame, and the function f(x) is used for calculation of the coefficient β.
Building on Claim 14, the function f(x), which helps calculate the coefficient beta for pixel dimming, is calculated as f(x) = (chromaAVE)^E. chromaAVE is the average saturation value of each pixel in the frame, and E is a coefficient between 0 and 2. This function uses the average saturation level of the frame to determine the pixel dimming amount.
16. The control signal generation circuit as claimed in claim 15 , wherein the coefficient E is set as 0.5.
In Claim 15, which describes the formula to determine pixel dimming, the coefficient E is set to 0.5. The function is calculated as f(x) = (chromaAVE)^0.5.
17. The control signal generation circuit as claimed in claim 1 , wherein the each-pixel saturation calculation circuit comprises: an each-pixel maximum value calculation section which calculates a maximum value of relative luminance of each pixel; an each-pixel minimum value calculation section which calculates a minimum value of the relative luminance of each pixel; an each-pixel saturation computing section which computes saturation of each pixel; an each-pixel maximum value judging section which judges whether the maximum value of the relative luminance of each pixel is larger or smaller than a maximum threshold value set in advance; and an each-pixel saturation value outputting section which outputs saturation values calculated when judged as being equal to or less than the maximum threshold value and when judged as being larger than the maximum threshold value, by the each-pixel maximum value judging section, respectively.
The pixel saturation calculation circuit from Claim 1 determines each pixel's saturation as follows: first it determines the maximum and minimum relative luminance values of each pixel. Next, the calculated saturation of each pixel is compared to a maximum threshold value. The pixel saturation value will differ based on the relative luminance being equal to or less than the maximum threshold value.
18. The control signal generation circuit as claimed in claim 17 , wherein the each-pixel saturation calculation circuit calculates the saturation value of each pixel as a saturation value that is smaller than an original saturation value in a case where the maximum value of the relative luminance of each pixel is equal to or less than the maximum threshold value.
In the saturation calculation process from claim 17, if the maximum relative luminance of a pixel is below the maximum threshold, the pixel's saturation is calculated to be *lower* than its original saturation value. This has the effect of reducing the color intensity of dimmer pixels, which prevents dim pixels from appearing overly saturated.
19. The control signal generation circuit as claimed in claim 18 , wherein provided that the saturation value of each pixel is defined as chroma, the maximum value of the relative luminance of each pixel is MAX, the minimum value of the relative luminance of each pixel is MIN, the maximum threshold value set in advance is F, and a coefficient within a range of 0≦G≦0.5 is G, the each-pixel saturation calculation circuit employs chroma=(MAX−MIN)/MAX under a condition of MAX>F while employing chroma=G under a condition of MAX≦F, and uses the values of chroma for the saturation value of each pixel.
Building on Claim 18, the display control circuit uses specific formulas to calculate pixel saturation. If a pixel's maximum relative luminance (MAX) is greater than a threshold F, its saturation (chroma) is calculated as (MAX - MIN) / MAX. If MAX is less than or equal to F, chroma is set to a constant G (0 <= G <= 0.5). This method sets a minimum saturation level (G) for pixels below the threshold.
20. The control signal generation circuit as claimed in claim 17 , wherein when the maximum value of the relative luminance of each pixel is equal to or less than the maximum threshold value, the each-pixel saturation calculation circuit calculates the saturation value of each pixel to become decreased continuously according to the maximum value of the relative luminance and to continue at the maximum threshold value.
Expanding on claim 17, if a pixel's maximum relative luminance is below a threshold, then the calculated saturation will continually decrease to match the maximum threshold. This contrasts with other cases in which the calculated saturation is fixed at a constant value.
21. The control signal generation circuit as claimed in claim 20 , wherein provided that the saturation value of each pixel is defined as chroma, the maximum value of the relative luminance of each pixel is MAX, the minimum value of the relative luminance of each pixel is MIN, and the maximum threshold value set in advance is F, the each-pixel saturation calculation circuit employs chroma=(MAX−MIN)/MAX under a condition of MAX>F while employing chroma=((MAX−MIN)/MAX)×(MAX/F) under a condition of MAX≦F, and uses the values of chroma for the saturation value of each pixel.
Building on claim 20, the display control circuit uses specific formulas to calculate pixel saturation. If a pixel's maximum relative luminance (MAX) is greater than a threshold F, its saturation (chroma) is calculated as (MAX - MIN) / MAX. If MAX is less than or equal to F, chroma is set to ((MAX - MIN) / MAX)*(MAX/F).
22. A video display device, comprising: the display panel; the backlight, and the control signal generation circuit claimed in claim 1 .
A video display device uses a display panel and backlight, and incorporates the control signal generation circuit described in Claim 1. The display controller adjusts pixel brightness based on video input, and intelligently dims the backlight to save power. Compensation is done on the pixels to enhance color quality.
23. A control signal generation method using a control signal generation circuit which comprises a first circuit unit which controls, according to an inputted video signal, light-up amount of each pixel of a display panel where a plurality of pixels constituted by including a white sub-pixel are disposed; and a second circuit unit which controls luminance of a backlight that lights up the display panel from a back surface, wherein: the first circuit unit supplements saturation of each pixel according to the light-up amount of the white-sub-pixel; the second circuit unit calculates a saturation value of each pixel; the second circuit unit calculates a saturation feature value in one frame by using the saturation value of each pixel; the second circuit unit calculates luminance decrease amount of the backlight based on the saturation feature value; the second circuit unit generates a signal for controlling the luminance of the backlight based on the luminance decrease amount of the backlight, and transmits the generated signal towards the backlight; the second circuit unit calculates a luminance increase rate of each pixel by using the saturation value of each pixel and the saturation feature value; and the first circuit unit performs luminance decreasing processing of each pixel according to the luminance increase rate, wherein when calculating the saturation feature value, the second circuit unit calculates the luminance decrease amount of the backlight as a small value in a case where the video signal is a case of a high saturation color display, calculates the luminance decrease amount of the backlight as a large value in a case where the video signal is a case of low saturation color display or a case of intermediate saturation color display containing primary color display in a part thereof, and calculates the luminance decrease amount of the backlight as a small value in a case where the video signal is a case of achromatic display containing primary color display in a part thereof.
This method controls display luminance and color saturation for a display panel that includes white sub-pixels (e.g., RGBW) and a backlight. It operates using a control circuit with two main units. The first unit processes the input video signal to control the light output of each pixel, including supplementing individual pixel saturation by adjusting the white sub-pixel's luminance. It also performs pixel-level luminance reduction based on a calculated rate. The second unit calculates the saturation value for each pixel and derives a frame-level "saturation feature value." Based on this feature, it determines how much to decrease the backlight's luminance: 1. A *small decrease* for high-saturation color video. 2. A *large decrease* for low or intermediate saturation color video (even if it contains primary colors). 3. A *small decrease* for achromatic (grayscale) video (even if it contains primary colors). This unit generates a control signal (e.g., PWM) for the backlight based on this decrease amount. It also calculates a luminance increase rate for each pixel, which the first unit uses to perform additional pixel luminance adjustments. ERROR (embedding): Error: Failed to save embedding: Could not find the 'embedding' column of 'patent_claims' in the schema cache
24. The control signal generation method as claimed in claim 23 , wherein when calculating the saturation feature value, the second circuit unit: judges whether the saturation value of each pixel is larger or smaller with respect to a saturation threshold value set in advance; individually calculates sum total of saturation deviation regarding a case where the saturation value is judged as being equal to or less than the saturation threshold value and a case where the saturation value is judged as being larger than the saturation threshold value, respectively; calculates a saturation deviation average value of total pixels by using the sum total of the each saturation deviation and number of resolution of the display panel; and calculates the saturation feature value by using the saturation deviation average value of the total pixels, a saturation maximum value of the total pixels, and a coefficient regarding luminance control of the backlight.
The method from Claim 23 for generating control signals calculates the "saturation feature value" as follows: It compares each pixel's saturation to a preset threshold. It calculates separate sums of "saturation deviation" above and below this threshold. These sums are then averaged to get a saturation deviation average for all pixels. Finally, it calculates the saturation feature value using this average, the maximum saturation value of all pixels, and a coefficient that controls how the backlight responds to saturation.
25. The control signal generation method as claimed in claim 23 , wherein when calculating the saturation value, the second circuit unit: calculates the maximum value of relative luminance of each pixel; computes the saturation of each pixel; judges whether the maximum value of relative luminance of each pixel is larger or smaller with respect to a maximum threshold value set in advance; and outputs the saturation value calculated, respectively, when judged as being equal to or less than the maximum threshold value and when judged as being larger than the maximum threshold value as a final saturation value.
The method described in Claim 23 determines pixel saturation as follows: First, it finds the maximum relative luminance of each pixel. Then calculates saturation of each pixel. Next, the calculated saturation of each pixel is compared to a maximum threshold value. The pixel saturation value differs based on the relative luminance being equal to or less than the maximum threshold value.
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May 27, 2015
July 18, 2017
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